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COPD: Donald Tashkin and Steven Kesten Long-term Treatment Benefits With Tiotropium in COPD Patients With and Without Short-term Bronchodilator Responses Chest 2003; 123: 1441-1449 [Abstract] [Full text] [PDF]

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No objective evidence for "poor responder" benefits

Jerzy M Giergiel   (22 August 2003)

No objective evidence for "poor responder" benefits 22 August 2003
Jerzy M Giergiel, Physisist unaffiliated Send letter to journal: Re: No objective evidence for "poor responder" benefits a984984{at}imap.cc Jerzy M Giergiel	Given tremendous socioeconomic and human impact of COPD it is important that any therapy claims be very carefully evaluated before they are advertised to public at large. Here Tashkin and Kesten conclude that bronchodilator therapy with tiotropium bromide "is effective irrespective of the presence or absence of a short-term response on the first day of treatment". Unfortunately nothing in their data appear to support this very optimistic conclusion. There are a number of criteria that are normally used in evaluation of effectiveness of bronchodilators in COPD. The traditional way is to simply evaluate bronchodilatory efficacy i.e. to look for effect in spirometric measures. 15% minimal improvement in peak response in FEV1 is typically required and by this standard only "responders" group showed effectiveness on all days of testing. "Poor-responders" failed that test on the first day by definition as they did on all other days for which the data are presented. No equivalent threshold criteria exist for trough response but in view of the above it is clear that "poor respondents" do not qualify here either. More recently a number of additional endpoints have been used in most clinical trials of bronchodilators. Some dyspnea index is usually included because this is how the profession rationalizes their widespread use in clinical practice. Mahler's transition dyspnoea index is commonly employed here with a threshold for clinically meaningful improvement set somewhat arbitrarily at 1 unit (1). Note this threshold is quite liberal; some 1 in 3 placebo patients reach or exceed it. Even by this relaxed standard, the "responders" group was again the only group that showed some efficacy here. Poor-responders failed again. Health-related-quality-of-life, another useful index was evaluated with St. George Respiratory Questionnaire. Here the commonly accepted clinical threshold is -4 units change in total score (2). By this standard, neither "responders" nor "poor-responders" showed satisfactory improvement with tiotropium bromide. It is not clear know how to interpret the additional efficacy data Tashkin and Kesten include in their paper. The change in albuterol use does not appear to have an established threshold value. In all fairness some improvement is observed here in both groups as it is in hospitalization and exacerbation data. Additional tests will be required before these potentially very useful indices can be confidently used. I view of the above, i.e. in view of the fact that no single efficacy test was met by the " poor-responders" group, it would be very useful to know what led the authors of this paper to conclude that tiotropium is effective irrespective of the presence or absence of a short-term response. J. Giergiel, Ph.D. 1. Clin Epidemiol. 2003 Mar;56(3):248-55. 2. Am Rev Respir Dis. 1992 Jun;145(6):1321-7.